1. Field of the Invention
The present invention relates to a Multi-Function Device (MFD) of a mobile terminal and particularly, to an apparatus and method for controlling a MFD of a mobile terminal to efficiently control the MFD according to operation modes of the mobile terminal.
2. Description of the Related Art
Recently, as mobile terminals are miniaturized and lightened, many components having many functions integrated to one component are used to miniaturize and reduce the number of components. A representative example of such an integrated component is a MFD.
The MFD is a component of a mobile terminal integrating functions of vibration, melody and speech and three functions of a vibration motor, buzzer and earpiece can be embodied in a single component. The MFD is divided into a voice coil and vibration coil having different resonance frequencies respectively. When a low vibration resonance frequency (fo) is inputted in the vibration coil, a vibration function is performed and when a voice band frequency is inputted in a voice coil, a voice is generated.
Therefore, when using the MFD, the manufacturing cost is reduced when compared to using conventional components. Also, when the MFD is efficiently used, the mobile terminal can have fewer components and thus can be miniaturized and lightened.
FIG. 1 is a view showing the apparatus for controlling the MFD of a mobile terminal in accordance with a conventional art.
As shown in FIG. 1, the apparatus for controlling the MFD of a mobile terminal includes a vocoder 10 for converting a digital voice signal inputted from the outside to a Pulse Code Modulation (PCM) signal, a codec 20 for encoding or decoding an output signal (PCM_out) of a vocoder 10, an audio amplifier 30 for outputting a driving signal (Audio_out) by amplifying/filtering an analog voice signal (Codec_out) outputted from the codec 20, a MFD 50 for respectively embodying reception of normal sound, melody and vibration functions according to the driving signal (Audio_out) of the audio amplifying unit 30.
The operation of the apparatus for controlling the MFD of a mobile terminal with the above structure, will be described as follows.
Firstly, the inputted digital voice signal is converted to a PCM signal (PCM_out) and inputted to the codec 20 by the vocoder 10. The codec 20 converts the PCM signal (PCM_out) to an analog signal (Codec_out) using a DAC (digital to analog converter) circuit (not shown) and outputs the signal to the audio amplifying unit 30. The audio amplifying unit 30 amplifies the inputted analog voice signal (Codec_out) to a certain level and adjusts the frequency response characteristic. Therefore, the MFD 50 can perform the speech, receiving sound and melody functions respectively according to the driving signal (Audio_out) of the audio amplifying unit 30.
Namely, the MFD 50 performs the vibration mode when the frequency of the driving signal (Audio_out) corresponds to a vibration frequency (fo) and outputs a sound having a response characteristic of the corresponding frequency when the frequency corresponds to another frequency bands. At this time, the codec 20 generates a sine wave form as the vibration frequency (fo) when a vibration mode is selected by a microprocessor, generates a wave form corresponding to a chord when of a melody mode is selected and a voice signal when a speech sound mode is selected.
FIG. 2A is a detailed circuit view showing the audio amplifying unit 30, including an audio amplifier 30A for amplifying the analog voice signal (Codec_out) of the codec 20 and an audio filter 40 for adjusting the frequency response characteristic of the amplified voice signal.
The amplifying gain and filter characteristic of the audio amplifying unit 30 is determined by the values of the resistors R1 and R2 of the audio filter 40 and values of the capacitor C1 and C2. Namely, the gain of the driving signal (Audio_out) is determined by the R2/R1 and as shown in FIG. 2B. The characteristic of the audio filter 40 has the characteristic of a band pass filter and the frequencies of the passband f1 and f2 are determined by the following formulas.f1=1/(2π*R1*C1)f2=1/(2π*R2*C2)
The passband frequencies f1 and f2 are generally set at about 300 Hz and about 3 KHz, respectively.
If the mobile terminal is set as a vibration mode, the codec 20 generates the vibration frequency (fo) of about 160 Hz under control of a microprocessor (not shown) and outputs the frequency. The vibration frequency (fo) of about 160 Hz is transmitted to the MFD 50 with the amplifying gain reduced in passing through the audio filter 40. Therefore, the MFD 50 is operated in the vibration mode by the transmitted vibration frequency (fo).
A problem may occur if the vibration force of the MFD 50 is weakened when the output of the vibration frequency (fo) inputted from the conventional audio amplifying unit to the MFD 50 is reduced to lower, than an optimum level. The set value of the passband may be set at about 200 Hz instead of about 300 Hz in order to prevent reduction of the output level of the vibration frequency (fo), thereby satisfying the vibration force of the vibration frequency (fo). However, the MFD 50 may generate unnecessary vibration if a low frequency component around 200 Hz is present in generating a melody or speech sound.
Namely, when processing all functions of receiving sound, melody and vibration, unnecessary vibration may be generated in the MFD, due to the low frequency components present in the driving signal typically generated by a busy signal and/or melody. Accordingly, adjustment of the sound volume is difficult since erroneous performance of the MFD may occur or the output level necessary for certain modes may not be satisfied.